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RECEPTORS AND SIGNAL TRANSDUCTION

Mechanisms of MAdCAM-1 gene expression in human intestinal microvascular endothelial cells

¹Division of Gastroenterology and Hepatology, ²Division of Pediatric Surgery, ³Department of Surgery, ⁴Digestive Disease Center, and ⁵Free Radical Research Center, Froedtert Memorial Lutheran Hospital, Milwaukee Veterans Administration Medical Center, Children's Hospital of Wisconsin, Medical College of Wisconsin, Milwaukee, Wisconsin

Submitted 22 September 2003 ; accepted in final form 29 September 2004

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is a homing receptor preferentially expressed on gut-associated endothelial cells that plays a central role in leukocyte traffic into the mucosal immune compartment. Although the molecular mechanisms underlying endothelial ICAM-1 or E-selectin expression have been intensively investigated, the mechanisms that regulate human MAdCAM-1 expression have not been defined. We report MAdCAM-1 gene and protein expression in primary cultures of human intestinal microvascular endothelial cells (HIMEC) that was not demonstrated in human umbilical vein endothelial cells. Similar to ICAM-1 and E-selectin expression, MAdCAM-1 gene expression in HIMEC was inducible with TNF-, IL-1, or LPS activation. However, in striking contrast to ICAM-1 and E-selectin expression, MAdCAM-1 mRNA and protein expression in HIMEC was heavily dependent on culture duration and/or cellular density, suggesting a prominent role for cell-cell interaction among these endothelial cells in the expression of the mucosal addressin. MAdCAM-1 expression was inhibited by both SN-50 (NF-B inhibitor) and LY-294002 [phosphatidylinositol 3-kinase (PI3-K) inhibitor], whereas ICAM-1 and E-selectin expression was inhibited by SN-50 but not by LY-294002. The Akt phosphorylation by TNF- or LPS was greater at higher cell density, demonstrating a pattern similar to that of MAdCAM-1 expression. NF-B activation was not affected by cellular density in HIMEC. MAdCAM-1 expression in human gut endothelial cells is regulated by distinct signaling mechanisms involving both NF-B and PI3-K/Akt. These data also suggest that PI3-K/Akt is involved in the gut-specific differentiation of HIMEC, which results in expression of the mucosal addressin MAdCAM-1.

cell adhesion molecules; nuclear factor-B; phosphatidylinositol 3-kinase

This article has been cited by other articles:

				J. Heidemann, W. Domschke, T. Kucharzik, and C. Maaser Intestinal microvascular endothelium and innate immunity in inflammatory bowel disease: a second line of defense? Infect. Immun., October 1, 2006; 74(10): 5425 - 5432. [Full Text] [PDF]